Document objects and attributes for the API.

This is just a start.
Revert "Use Ruby 2.1."

This reverts commit a6bde79b86eed8f51b363cbb520f04096274bf34.
Start properly mocking out the API.

Now I know the Apiary format a bit more it's easier to do this stuff.
Stub out most of the API methods.

I'm still struggling with Apiary a little bit, it seems like there's lots of repetition and the format isn't particularly free form. I think this structure is "good enough" to get to a point where everybody understands what's going on.
More touch ups.
Fleshing out the messages API docs more.

Specifically adding versioning to the content-type, making the lists just, actually lists and making the params just a string.